The purpose of this training program is to mentor the next generation of behavioral scientists with expertise in substance abuse and its relationship with HIV and other infectious diseases, especially viral hepatitis, TB and sexually transmitted infections (STls). Our program will build upon the joint doctoral programs in epidemiology, health behavior and clinical psychology offered through a longstanding partnership between the University of California San Diego (UCSD) School of Medicine and the San Diego State University (SDSU) Graduate School of Public Health and College of Arts and Sciences. Our objectives are: 1) To provide opportunities for interdisciplinary research training experiences for pre-doctoral students and postdoctoral fellows in epidemiology, health behavior and psychology who wish to focus their research in the intersection between substance abuse and HIV or other infectious diseases (e.g. viral hepatitis, TB, STls);2) To offer students hands-on experience in the study of HIV and related infectious diseases in international settings which bear the greatest burden of injection drug use, HIV and related infections;3) To recruit and train researchers from diverse academic backgrounds and under-represented minority populations with skills needed to become independent behavioral scientists with state-of-the-art skills to address challenges in substance use and HIV-related research;4) To train individuals in the ethical conduct of research with human subjects, especially in international and cross-cultural settings. The directors of our training program are renowned for their experience with behavioral interventions among drug using populations, focusing on both primary and secondary prevention, and have an exemplary record of mentoring females and underrepresented minorities. Our proposed program will provide support for three predoctoral and three postdoctoral trainees, who will be mentored by pairs from among 15 Core Faculty who represent diversity in research interests, specific skills (e.g., epidemiology, psychology, neuropsychology, genetics, biostatistics, health promotion and global health), professional background (M.D., Ph.D.), gender, ethnicity, and seniority. Trainees are required to complete courses in substance abuse and infectious diseases, instruction in responsible conduct of research, quarterly cultural sensitivity training workshops, monthly journal club and 'work In Progress'seminars and an annual grant-writing workshop. San Diego is arguably the largest U.S. city in close proximity to a developing country (i.e., Mexico), creating the opportunity for hands-on training experiences that can be transported elsewhere as trainees develop into independent investigators.